What Is Variable Valve Timing?

What Is Variable Valve Timing?

In a traditional engine, the positions of the crankshaft and camshaft(s) are fixed towards each other. This means that each valve opens and closes at the same time and remains open or closed for a set period of time no matter how hard or fast the engine is running. Such technology is perfect for smooth engine operation, yet doesn’t allow for getting the most out of the engine, especially if the vehicle is towing something or going up hills. To solve this problem, many modern engines come equipped with variable valve timing, which makes it possible to adjust valve timing on the go.

As its name may suggest, the variable valve timing technology (VVT) allows for changing the position of the camshaft(s) and, therefore, the time when the related valves are opened and closed. This can be done in a couple of ways, all of which, however, do the same thing, adjusting the valve timing depending on the engine speed. The name this technology comes with in a specific vehicle may also vary based on its make and model. Thus, the other popular names are variable valve timing with intelligence (VVT-I) and variable camshaft timing (VCT).

The most common variable valve timing technology is known as camshaft phasing. It allows for adjusting the camshaft position with engine speed. This also automatically changes the valve timing since the valves are operated by the camshaft. Just like almost everything else in a modern vehicle, camshaft phasing is controlled by the engine control unit, which relies on the camshaft and crankshaft position sensors to monitor the positions of the shafts. As a rule, the vehicle’s computer controls and operates one of the camshafts, however, there are vehicles with both operable camshafts. The newest and most technology advanced vehicles can also come with variable valve lifting and variable valve duration.

The variable valve timing technology is aimed at improving engine performance and fuel efficiency. That’s why any problems related to VVT operation can cause a lack of engine power and increased fuel consumption. To prevent this from happening, we would like to draw your attention to the most common symptoms of a failing VVT system:

Reduced engine performance 

Rough idling, poor acceleration, hesitation and other performance problems can be signs of problems with the VVT system.

Increased fuel consumption

Improper engine operation is synonymous with poor fuel economy. If you have to spend more and more at the pump, you should check the condition of your VVT system.

High emissions

Vehicles equipped with VVT often rely on this system to handle exhaust gas recirculation. That’s why its failure can increase emissions.

Abnormal noises

If you hear any rattling or tapping noises coming from the engine, you might have a stretched timing chain or a bad camshaft actuator.

Your check engine light is on

The engine control unit monitors your VVT operation. If it detects any problem, it will turn on the check engine light.

VVT troubleshooting

The variable valve timing system is very complex, which is why it must be diagnosed and repaired by a professional. Besides, this often involves specific equipment, such as special scanners or similar tools you may not have. Although, there is something you can do on your own to prevent VVT problems. You should follow the manufacturer’s recommended maintenance plan and schedule to keep your vehicle running safely and smoothly as long as possible. Regular oils changes and keeping the oil level at or near max can save you a lot of money and headache in the long run.